The present invention relates to the field of electrical devices, and, more particularly, to transformers for a static converter and transformer-rectifier units.
In transformer-rectifier units, transformers are generally used whose primary and secondary windings are coaxial, i.e., superimposed in the radial direction. These windings are made with enameled wire or with copper hoops (i.e., planar winding). Another example is the axial stack system which has been described, for example, in French Patent 1,028,950A to C. Gosselin. This patent discloses the use of copper segments appropriately slotted to form a turn that can be placed around a core for single-phase or tri-phase transformers at 50 or 60 Hz.
U.S. Pat. No. 4,965,712 to Duspiva et al. also discloses turns formed from a cutout copper sheet, but with a core making multiple turns around the copper segment. This transformer is intended for use in a high-frequency circuit.
The two prior art systems described above integrate rectification diodes between the secondary segments. They share the disadvantage of having a high leakage inductance, which may limit the usage frequency and subsequently make the system large, heavy and expensive.
An object of the invention is to provide a high-frequency transformer which has a relatively simple structure and is relatively inexpensive to manufacture.
In accordance with the invention, a high-frequency transformer may include integrated rectifiers and primary and/or secondary windings including conductive segments surrounding a single branch of the magnetic core, and which preferably operates at a frequency between 3 and 50 kHz. The transformer may further include silicon rectification diodes, which may be implemented in relatively thin chips, directly between the conductive segments (which may be cooper or aluminum, for example). The transformer may also include an alternating stack on the core branch including flat windings and conductive plates alternated several times.
In addition, the rectification may be performed using a two-phase type circuit with two diodes and a secondary winding at a midpoint, a classical bridge, or with a circuit with two filter inductances. Furthermore, the rectification diodes may be securely positioned between the conductive segments forming the secondary windings and collecting segments to assure good thermal and electrical contact.
The collecting segments and the conductive segments may advantageously be cooled by circulating air or by circulating water in the segment using channels, for example. Furthermore, the conductive segments may be used as the primary winding, either directly by placement in series using conductive columns, which may be arranged in quincunx fashion, or the conductive segments may be U-shaped and used as the primary winding. A bridge switching generator may be connected to the conductive segments and include four switches arranged between continuous power supply segments, and the bridge pattern may be repeated several times. The power supply segments may be inserted between the windings or the plates that are used as the secondary winding.
In addition, the conductive segments may be secondary windings, and the rectifier may be formed by connecting the midpoints using conductive columns, along a first axis xcex941, while the diodes are stacked along a second axis xcex942. The diodes may also be positioned at the midpoints. Further, the flat windings may be made with enamel wire with two superimposed spirals connected at their center (one being centripetal and the other centrifugal), or by two copper plates cut in spiral fashion and connected together by a weld in the center of the winding, for example. Also, the conductive plate may include a flat thermal diode.
The invention may advantageously be used for constructing static converters, either for voltage step-up or for step-down. Moreover, the invention may also be used to power TIG, MIG, ARC, and/or spot welding machines, as well as for plasma machines for zinc plating, plasma cutting, etc.